RESUMO
Latent infection of primary CD34(+) progenitor cells by human cytomegalovirus (HCMV) results in their increased survival in the face of pro-apoptotic signals. For instance, we have shown previously that primary myeloid cells are refractory to FAS-mediated killing and that cellular IL-10 (cIL-10) is an important survival factor for this effect. However, how cIL-10 mediates this protection is unclear. Here, we have shown that cIL-10 signalling leading to upregulation of the cellular factor PEA-15 mediates latency-associated protection of CD34(+) progenitor cells from the extrinsic death pathway.
Assuntos
Infecções por Citomegalovirus/metabolismo , Citomegalovirus/fisiologia , Proteína Ligante Fas/metabolismo , Interleucina-10/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Células Mieloides/virologia , Fosfoproteínas/metabolismo , Células-Tronco/virologia , Latência Viral , Antígenos CD34/metabolismo , Apoptose , Proteínas Reguladoras de Apoptose , Linhagem Celular , Citomegalovirus/genética , Infecções por Citomegalovirus/genética , Infecções por Citomegalovirus/fisiopatologia , Humanos , Interleucina-10/genética , Peptídeos e Proteínas de Sinalização Intracelular/genética , Células Mieloides/citologia , Células Mieloides/metabolismo , Fosfoproteínas/genética , Células-Tronco/citologia , Células-Tronco/metabolismoRESUMO
A subset of viral genes is required for the long-term latent infection of hematopoietic cells by human cytomegalovirus (HCMV). Here, we show that a latency-associated gene product (LUNA) promotes the disruption of cellular PML bodies during latency. Mutation and inhibitor studies reveal that LUNA encodes a deSUMOylase activity responsible for this disruption. Specifically, LUNA encodes a conserved Asp-Cys-Gly motif common to all deSUMOylases. Importantly, mutation of the putative catalytic cysteine is sufficient to reverse LUNA-mediated PML dispersal and markedly reduces the efficiency of viral reactivation. The depletion of PML from cells is sufficient to rescue the reactivation of the LUNA-deficient viruses, arguing that targeting PML is an important biological role of LUNA. Finally, we demonstrate that reactivation of naturally latent HCMV is blocked by deSUMOylase inhibitors. Thus, latent HCMV primes the cellular environment for efficient reactivation via the activity of a virally encoded deSUMOylase.
Assuntos
Citomegalovirus/fisiologia , Proteínas Virais/metabolismo , Ativação Viral/fisiologia , Latência Viral/fisiologia , Sequência de Aminoácidos , Antígenos CD34/metabolismo , Carbono-Nitrogênio Liases/química , Carbono-Nitrogênio Liases/genética , Domínio Catalítico , Células Dendríticas/metabolismo , Células Dendríticas/virologia , Humanos , Corpos de Inclusão/metabolismo , Mutação/genética , Células THP-1RESUMO
The transcription factor T-bet directs Th1 cell differentiation, but the molecular mechanisms that underlie this lineage-specific gene regulation are not completely understood. Here, we show that T-bet acts through enhancers to allow the recruitment of Mediator and P-TEFb in the form of the super elongation complex (SEC). Th1 genes are occupied by H3K4me3 and RNA polymerase II in Th2 cells, while T-bet-mediated recruitment of P-TEFb in Th1 cells activates transcriptional elongation. P-TEFb is recruited to both genes and enhancers, where it activates enhancer RNA transcription. P-TEFb inhibition and Mediator and SEC knockdown selectively block activation of T-bet target genes, and P-TEFb inhibition abrogates Th1-associated experimental autoimmune uveitis. T-bet activity is independent of changes in NF-κB RelA and Brd4 binding, with T-bet- and NF-κB-mediated pathways instead converging to allow P-TEFb recruitment. These data provide insight into the mechanism through which lineage-specifying factors promote differentiation of alternative T cell fates.